Customer loyalty cards are traditionally embodied as plastic cards with magnetic stripes that are readable by a magnetic card reader operatively coupled to a checkout terminal, such as a cash register. Such plastic loyalty cards involve certain problems. For example, administration and mailing of the cards is a labour-intensive operation for the issuing companies. Furthermore, the necessity of carrying around a number of physical cards is a burden on the consumers. US patent application 2009/0012900, titled “Making Secure Data for Customer Loyalty Programs” addresses various techniques for implementing electronic loyalty cards.
Replacement of the traditional loyalty cards by their electronic equivalents poses new security threats, particularly if the benefits provided by the various loyalty cards are supposed to be variable, which means that some loyalty cards provide benefits not provided by others. Obviously, the loyalty cards should be tamper-proof, which goal is typically reached by means of cryptographic techniques. But the use of cryptographic techniques and a feature set which depends the customer and the technical parameters of the customer's terminal involves problems that are not adequately addressed in the prior art.